(Natural) Death is Evolutionarily Absurd

Why the evolutionary origin of senescence is a mystery:

From an evolutionary perspective, individuals that do not senesce would have a tremendous reproductive advantage. So why hasn’t natural selection eliminated senescence?

Link to paper

The death rates at extreme old ages start to slow down, which is the opposite of what would be expected if death by aging was programmed. From an individual-selection point of view, having genes that would not result in a programmed death by aging would displace genes that cause programmed death by aging, as individuals would produce more offspring in their longer lifespan and they could increase the survival of their offspring by providing longer parental support.

Gavrilov, Leonid A; Gavrilova, Natalia S. (7 February 2002). "Evolutionary Theories of Aging and Longevity". TheScientificWorldJOURNAL 2 (2): 339–356.

originally posted by: Astyanax
That was explained earlier. Have a nice thread.

You explain nothing. Organisms with zero lifespan will have zero time to develop evolution strategy. Your argument is not only moot, it is highly naive. Evolutionary scientists have already pointed out that higher lifespan would actually benefit evolution, directly disproving your argument, but you seem hellbent on ignoring their logic.

Saying that living beings die because "they evolve better if they die" is stupid - according to such a logic, after the hundred of milions of years life had to develop, all animals would have evolved to live only seconds by now.

Care to try again? Or perhaps you have no interest in using actual critical thinking skills? Stars above your post are not everything, you know.

a reply to: swanne

It's not like the scientific community is in consensus about those things. There is still much debate and much to learn and study. Like you said, it's still a mystery.

Aging varies depending on the organism, and many do not live much longer than reproduction. I don't mean any offense by this, but it seems a bit simplistic to say that longer life automatically means better reproductive success. First, there is less genetic diversity that way. 2nd, Humans females go through menopause on average at age 51, so anything beyond that is 100% irrelevant to evolution.

Plus with sexual selection being a factor, combined with the fact that most humans reproduce in their 20s and 30s when their sex drive is high; older folks generally have less sex and don't try to reproduce when they are older than 40 because it can lead to complications. Higher lifespan does not necessarily mean more evolutionary success, and without modern medicine, most humans don't live past 60 regardless.

The other big factor that seems to have been forgotten here is that evolution DOES NOT GUARANTEE improvements. Evolution doesn't have an end game, nor does it have goals or always make something better. That is a common misconception. There are random mutations in the genetic code, and either they offer an advantage, they are neutral, or they offer a disadvantage. To suggest evolution should have eliminated aging by now is nonsensical. It's like suggesting that evolution should have given us wings by now or should have made us all psychic by now because it would help tremendously. It doesn't work that way. First the mutation has to happen, second it has to be selected for.

a reply to: Barcs

I wholeheartedly agree with your entire post, well said indeed. More people (such as the one who thinks that evolution is somehow "threatened" by longer lifespan) should read from it, it describes quite accurately the actual bigger picture.

Aging varies depending on the organism, and many do not live much longer than reproduction. I don't mean any offense by this, but it seems a bit simplistic to say that longer life automatically means better reproductive success. First, there is less genetic diversity that way. 2nd, Humans females go through menopause on average at age 51, so anything beyond that is 100% irrelevant to evolution.

Less genetic diversity is an excellent argument, thank you for raising that point. You could be right about that... Although I would tend to think that organisms which live longer would also have more chance breeding with more individuals of the same species (not every species are monogamous! ), effectively augmenting genetic diversity within the species. This is of course just pure speculation on my part.

As for menopause, this varies greatly between species, so I agree with you: in species with early menopause, anything after is indeed irrelevant. However in species with late or nonexistent menopause, the matter may still be relevant.

a reply to: Barcs

Does anybody really ever die from "natural causes", though? Usually it's something that directly kills them like a heart failure or a sickness that wreaks havok and the body can't handle it when it's that old. Old age itself doesn't seem to kill, it just makes the body weaker over time and more susceptible to other issues. I still maintain my original view... ageing is completely irrelevant to evolution because it has nothing to do with passing down genes.

I agree that natural selection cannot operate on non-heritable traits. That’s the nub of your argument.

Death and cellular immortality, however, are heritable traits.

With your interest in biology, I’m a little surprised you don’t already know this, Barcs, but the arc of life is carefully controlled by gene expression. A vital — so to speak — feature of this process is apoptosis, the programmed death of cells, which occurs continuously, in a controlled manner, throughout life. The function of apoptosis is to kill off unwanted or potentially threatening cells so that the organism can continue to live and develop, thus contributing to the longevity and development of the genome — the set of specific genes it carries, together with other members of its species.

Telomere shortening, at the end of life, seems also to be an evolved process. It must be, because it is not present in single-celled organisms. Its function is to kill off entire organisms, just as apoptosis kills off individual eukaryotic cells, and for precisely the same reason; to ensure the survival and optimal evolutionary development of the genome.

You are absolutely right that natural selection cannot and does not operate on infertile organisms. Bodies and faculties weaken after they pass reproductive age because there is no selective benefit accruing to the genome from continued survival. Yet natural selection is by no means blind to the competition for resources between young organisms and older ones. Apoptosis shows us that genes have evolved to kill off unwanted cells. Telomere shortening and diseases like cancer — which is what happens when apoptosis ceases to work correctly — may well be evolved responses to the same problem.

Swanne, you might find the following article about how cancer arises interesting. Death evolved because evolution is necessary to life, and immortality is incompatible with evolution. I trust this is now clear.

a reply to: ShadeWolf

ou can see examples of this (as well as examples of creatures literally breeding themselves to death) in a number of animal species, the best example of which is probably the mayfly. In its mature form, the mayfly exists solely to breed, not even being able to eat, with a lifespan of a day at most.

Thank you for reminding us of mayflies. They are an excellent example of a species that evolution has designed for optimal mortality in order to maximize survival and reproduction opportunities for descendants and hence for the genome.

a reply to: swanne

Some other extracts from the first link you quoted:

An alternative theory is that senescence is driven by a genetically regulated, programmed process with hormonal mechanisms as its pacemaker. Recent work has focused on neuroendocrine signaling that may account for increased longevity associated with caloric restriction...

Senescence is the price we pay for vigour and reproductive fitness in our youth. The humbling takeaway is that natural selection optimizes our reproductive fitness, not our health or lifespan.

Your second quote is from Wikipedia, not from the source you cite. Are you trying to deceive us?

The actual paper you cite, the one by the Gavrilov and Gavrilova, does not contain the text you ‘quote’. It does, however, contain the following interesting passage:

The search for the trade-offs between longevity and reproduction was made also in experiments with soil-dwelling round worms where a number of long-lived mutants have been identified. When long-lived mutants were reared together with normal (wild-type) individuals under standard culture conditions, neither of them exhibited a competitive advantage, contrary to theoretical evolutionary predictions. Only when cultures were exposed to starvation cycles (alternatively fed and starved, mimicking field conditions in nature) did the wild-type worms outcompete (outnumber) the long-lived mutant.
These findings demonstrate that increasing lifespan may exhibit some fitness cost only in harsh conditions (cycles of severe starvation), thereby providing limited support for the antagonistic pleiotropy theory of ageing.

The Gavrilovs are researchers into ageing, not evolutionary theorists, and they are somewhat antagonistic to evolutionary theories (like the one Barcs is supporting) that suggest evolution is hostile to longevity. Yet even they are forced to admit that, under wild conditions, longevity is a liability over several generations. There is — also — no need to invoke group selection to explain this.

I would say the reason we don't have a perfect self repairing system is that evolution has no reason to develop such a mechanism. If some of the first cave men were still alive it would be bad for our species, their DNA is now obsolete compared to the DNA of modern man. If organisms never died then they would never change or evolve. There are however a few organisms known to science which appear to be immortal, so it's definitely possible, it's just not very beneficial because it doesn't motivate the production of offspring, so not many species will be like that.

a reply to: swanne

Saying that living beings die because "they evolve better if they die" is stupid - according to such a logic, after the hundred of milions of years life had to develop, all animals would have evolved to live only seconds by now.

It's not stupid at all, organisms will evolve better if they die, but that doesn't mean they should die as quickly as possible. If an organism ages it is under pressure to produce offspring before it dies, it has some limited time to propagate its DNA and then it must die. If it lives forever and continues injecting its DNA into the population it wont have any real benefit in terms of evolution and could even hold back development of the species. Being immortal isn't enough to survive forever, a species must also be constantly adapting to environmental conditions and predators.

If I'm writing a genetic algorithm to simulate evolution I'm most certainly going to enforce an age limit on the virtual creatures because members of the first few hundred generations are going to be quite terrible. Over time they will evolve and the offspring of each generation should ideally be a bit better than their parents. Of course evolution doesn't always go in one direction though, and it's very possible for the offspring to perform worse than their parents. If the algorithm is well designed though, the virtual creatures should get better over the long term.

a reply to: ChaoticOrder

There are however a few organisms known to science which appear to be immortal, so it's definitely possible, it's just not very beneficial because it doesn't motivate the production of offspring, so not many species will be like that.

You are absolutely correct.

Evolution occurs for the benefit of genes, not the organisms that carry them. Organic immortality is dangerous because it threatens the survival and propagation of genes.

a reply to: Astyanax

But evolution is not supposed to occur for the "benefit" of anything, lest you wade into teleological waters.

And correct me if I'm wrong, but hasn't Dawkins' SGT been rendered mostly useless?

a reply to: PhotonEffect

Astyanax: Evolution occurs for the benefit of genes

PhotonEffect: But evolution is not supposed to occur for the "benefit" of anything

Quite right, and thank you for the correction. I should have said, and meant to say, that it is ultimately genes, that are subject to selection for optimal survival and reproduction. I used a convenient shorthand — and shouldn’t have.

a reply to: Astyanax

Swanne, you might find the following article about how cancer arises interesting. Death evolved because evolution is necessary to life, and immortality is incompatible with evolution. I trust this is now clear.

This is your opinion, nothing more. Maybe it's all settled in your head, but in the actual science world, the question is still under investigation.

Please, please try to see the logical hole in your argument! If longevity is incompatible with evolution, and since animals & plants had hundreds of millions of years to evolve, then how come all animals & plants don't die within minutes after reproduction? Some mayflies do die after a few days, but then most other insects of similar profile do not - in fact mayfly lifespan is anomalous when compared to other insects (may they be more recent or more ancient genera of insects) - which means that the process (whatever it is) that forces mayflies to die so quick does not apply to most other insects. Furthermore, galapagos turtles evolved to live over a century, many trees evolved to live thousands of years, and some medusa even evolved to become biologically immortal.

How do you explain that??

As for cancer: your cancer thing does not prove your assumption that evolution is trying to kill living beings using cancer. In fact, since cancer cells are basically immortal by themselves, it disproves your own conclusion. It could very well be that nature is (albeit clumsily, since blind genetic modification is it only tool) attempting to create pluricellular organisms whose cells can reproduce forever. We already know that newt regenerative cells (the cells that enables newts to grow entire new limbs from scratch) ar strongly similar to human cancer cells.

Regeneration as Controlled Cancer

a reply to: Astyanax

I should have said, and meant to say, that it is ultimately genes, that are subject to selection for optimal survival and reproduction.

"Optimal" is another unfortunate word here. This is not meant to criticize you, rather to point out that it is not always easy to find language to describe evolution without suggesting, either indirectly or directly, a teleological outcome.

Besides that, most genes don't operate in isolation but more so in complex networks – either pleiotropically, polygenically, or both. So how do we reasonably determine which gene was selected for and why under these circumstances?

originally posted by: PhotonEffect
"Optimal" is another unfortunate word here. This is not meant to criticize you, rather to point out that it is not always easy to find language to describe evolution without suggesting, either indirectly or directly, a teleological outcome.

Still throwing around those semantic arguments, eh? I think you knew darn well what he was saying. The outcome only becomes teleological when you blatantly misinterpret the language used. He was referring to natural selection of the more favorable genes. Evolution does follow a direction... the direction of the environment (no I'm not saying nature is the director of an orchestra, hence designed).

a reply to: Barcs

Still throwing around those semantic arguments, eh?

Is that all you got Barcs?

Astyanax doesn't need you to fight his battles for him. Nice of you to think so, but he's much more equipped than you or me for that matter to handle his own.

The direction of the environment? Good one, bro.

a reply to: PhotonEffect

This is not meant to criticize you, rather to point out that it is not always easy to find language to describe evolution without suggesting, either indirectly or directly, a teleological outcome.

Very true, although I would regard this as a shortcoming of the way our brains work rather than as an argument for a Creator.

originally posted by: PhotonEffect
a reply to: Barcs

Still throwing around those semantic arguments, eh?

Is that all you got Barcs?

Astyanax doesn't need you to fight his battles for him. Nice of you to think so, but he's much more equipped than you or me for that matter to handle his own.

The direction of the environment? Good one, bro.

I'm not trying to fight anyone's battles, this is a public discussion forum in which anybody can participate. I'm merely making observations on your posts which seem to repeatedly twist the meanings of words to suggest evolution is incomplete or unreliable. No, I think that is all YOU have.

You are doing the same exact thing in the thread with Phantom423 as well and you've nitpicked me a bunch of times on terminology semantics. The only one making things teleological is you. I just don't really see what you are trying to accomplish by constantly making those types of arguments. Of course natural selection and evolutionary fitness is determined by the environment...

Oh wait I used the word "determined." How can something be determined without one to determine.

Here's a scientist who has studied the subject of cell death, perhaps her conclusions can be of help:

originally posted by: Barcs
I'm merely making observations on your posts which seem to repeatedly twist the meanings of words to suggest evolution is incomplete or unreliable. No, I think that is all YOU have.

Not an accurate interpretation of your observations, friend. I wasn't twisting anyone's words, although you do like to think that's what it was. I was pointing out issues with using certain words. My alleged insistence to "nitpick' as you put it, is meant to shed light on the language in biology as being very loose and misleading. Dawkins' entire theory is built on a steady diet of metaphor and hyperbole. It's a nice story which people eat up, but they also think this is how genes and evolution should be looked at — even if it's wrong.

originally posted by: Barcs
You are doing the same exact thing in the thread with Phantom423 as well and you've nitpicked me a bunch of times on terminology semantics. The only one making things teleological is you. I just don't really see what you are trying to accomplish by constantly making those types of arguments.

It's not my fault some folks can't see past their nose.